Conventional manufacturing technologies for semiconductor integrated circuits may include processing of silicon wafers, often referred to as substrates, in fully automated vacuum cluster tools. See e.g., U.S. Pat. Nos. 5,882,413, 6,208,751, and 6,451,118, each incorporated by reference herein. A typical cluster tool may include a circular vacuum chamber with load locks and process modules connected radially to the circumference of the chamber in a star pattern. The tool is typically serviced by a vacuum environment robotic manipulator (robot) which is located near the center of the chamber and cycles the substrates from the load locks through the process modules and back to the load locks. Another robot may be located in an atmospheric transfer module which serves as an interface between the load locks of the vacuum chamber and standardized load ports serviced by an external transportation system.
A conventional vacuum environment robotic manipulator typically includes a drive unit which houses all active components of the robotic manipulator, e.g., actuators and sensors, and one or more arms driven by the drive unit. The arm(s) are typically passive mechanisms, i.e., they do not include any active components, such as actuators and sensors. This is primarily due to difficulties with out-gassing, power distribution and heat removal in vacuum environments.
Typical vacuum environment single-end-effector arm designs for a conventional cluster tool chamber include telescoping. See e.g., U.S. Pat. Nos. 4,715,921 and 5,404,894, SCARA-type, e.g., U.S. Pat. No. 5,765,983, and frog-leg mechanisms, e.g., U.S. Pat. No. 4,730,976, all of which are incorporated by reference herein. The drawbacks of a star configuration of a conventional cluster tool chamber may include a relatively large footprint and inconvenient interface geometry. In response to the growing demand for footprint reduction, tools with stations arranged in a non-radial manner have been introduced. In order to access non-radial (orthogonal) stations properly, the vacuum environment robotic manipulator needs to be capable of moving and positioning the end-effector to a given point with a specified orientation, i.e., providing three degrees of freedom in the plane of operation. An example concept of such a planar 3DOF robot arm was disclosed in U.S. Pat. No. 7,245,989, incorporated by reference herein.
In many applications, a vacuum environment robotic manipulator is required to replace a processed substrate with a fresh substrate. This operation, typically referred to as a substrate exchange, often directly affects the throughput performance of the cluster tool, i.e., the number of substrates processed by the tool per hour. In order to complete a substrate exchange operation, a single-end-effector robotic manipulator typically picks the processed substrate from the workstation, places it to a specified location, picks a fresh substrate from another location, and places it to the workstation. This sequence typically requires a total of thirteen discrete moves. The number of moves, and thus the substrate exchange time, may be improved substantially by utilizing a robot with two or more end-effectors. See e.g., U.S. Pat. Nos. 5,180,276, 5,647,724, 6,485,250, and U.S. Publ. No. 2006/0099063, all of which are incorporated by reference herein. In these examples, the robot picks the processed substrate by one end-effector and replaces it by a fresh substrate readily available on another end-effector, thus reducing substantially the number of moves on the critical path.
While atmospheric environment robots often utilize various substrate grippers, the arm(s) of the vacuum environment robotic manipulators are passive mechanisms and therefore typically hold the substrate subject to processing solely by the means of frictional forces between the substrate and the robot end-effector. Since the inertial force at the substrate cannot exceed the holding force securing the substrate to the end-effector in order to prevent undesirable slippage, the acceleration of the end-effector carrying a substrate needs to be limited, which in turn may limit the throughput performance (number of substrates processed per hour) of the vacuum environment robotic manipulators.
Therefore, it is advantageous to provide a vacuum-compatible robot gripper system, such as an active edge-clamping mechanism, that would eliminate the acceleration constraint due to substrate slippage and allowed for an increased throughput performance of the vacuum environment robots.